Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• acetal group could be used as substrates in an aza-Nazarov cyclization with the intermediacy of in situ-generated N-acyliminium ions (Scheme 1b) [21]. The first catalytic aza-Nazarov reaction was reported by Tius and co-workers in 2010, which involved the kinetic resolution of azirine derivatives via an

Electrochemical Friedel–Crafts-type amidomethylation of arenes by a novel electrochemical oxidation system using a quasi-divided cell and trialkylammonium tetrafluoroborate

• Hisanori Senboku,
• Mizuki Hayama and
• Hidetoshi Matsuno

Beilstein J. Org. Chem. 2022, 18, 1040–1046, doi:10.3762/bjoc.18.105

• 1,3,5-trimethoxybenzene or indoles in DMA containing 0.1 M iPr2NHEtBF4 using an undivided cell equipped with a Pt plate cathode and a Pt wire anode (a quasi-divided cell) resulted in selective formation of N-acyliminium ions of DMA at the anode, which reacted with arenes to give the corresponding

• amidomethylated products in good to high yields. Keywords: electrochemical oxidation; Friedel–Crafts type amidomethylation; N-acyliminium ion; quasi-divided cell; trialkylammonium salt; Introduction Oxidation of amides generates useful intermediates, N-acyliminium ions, which have been widely used in organic

• synthesis [1][2][3][4]. For example, Friedel–Crafts-type amidomethylation [5][6][7][8][9][10][11][12][13][14][15] proceeds efficiently by the reaction of N-acyliminium ions with electron-rich arenes to give the corresponding amidomethylated products in good yields. Since amides are important intermediates

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

• through inductive effects, and on amides, which should be more prone to engage in the cyclization owing to the high reactivity of expected N-acyliminium ions 4a (R1 = alkyl, R2 = acyl) in SEAr reactions. In the second screening round, we determined the isolated yields of the promising reactions identified

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• imides and no racemization was observed during the reaction (Scheme 50). In 2000, Pilli and co-workers published a vinylogous Mannich addition of silyloxyfuran to chiral N-acyliminium ions generated in situ from 157 which had been obtained from the anodic oxidation of 156 bearing a cyclohexyl-based

• chiral auxiliary ([92]. The authors established that the Mannich addition occurred exclusively on the Si-face of the N-acyliminium ions, resulting in the threo-isomer as the major isomer (with moderate yields and good diastereomeric ratios). Upon catalytic hydrogenation followed by methanolysis, threo

• -158a, and 159a were further converted to the corresponding lactams 160a and 160b enabling efficient recovery of chiral auxiliaries (Scheme 51). Furthermore, the same group reported an identical method for the TiCl4-promoted addition of allyltrimethylsilane to N-acyliminium ions containing the same

Stereoselective nucleophilic addition reactions to cyclic N-acyliminium ions using the indirect cation pool method: Elucidation of stereoselectivity by spectroscopic conformational analysis and DFT calculations

• Koichi Mitsudo,
• Junya Yamamoto,
• Tomoya Akagi,
• Atsuhiro Yamashita,
• Masahiro Haisa,
• Kazuki Yoshioka,
• Hiroki Mandai,
• Koji Ueoka,
• Christian Hempel,
• Jun-ichi Yoshida and
• Seiji Suga

Beilstein J. Org. Chem. 2018, 14, 1192–1202, doi:10.3762/bjoc.14.100

• , Okayama 700-8530, Japan Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan 10.3762/bjoc.14.100 Abstract In this study, six-membered N-acyliminium ions were generated by the “indirect cation pool” method and

• reacted with several nucleophiles. These reactions afforded disubstituted piperidine derivatives with high diastereoselectivities and good to excellent yields. The conformations of the obtained N-acyliminium ions were studied by low temperature NMR analyses and DFT calculations and were found to be

• pool” method can realize the generation and accumulation of highly reactive cationic species such as N-acyliminium ions in relatively high concentrations by low temperature electrolysis [6][7][8][9][10]. The N-acyliminium ions thus generated can directly react with a variety of carbon nucleophiles to

Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions

• Jixin Liu,
• Srimoyee Dasgupta and
• Mary P. Watson

Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290

• -component coupling of pyridine, benzoyl chloride and phenylacetylene [27], the Arndtsen group tackled the challenge of developing a catalyst for the alkynylation of cyclic N-acyliminium ions with unactivated alkynes [28]. Using the reaction of N-acylquinoline and phenylacetylene as their model, they

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

• Alan M. Jones and
• Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

• Alan M. Jones Craig E. Banks Manchester Metropolitan University, Faculty of Science and Engineering, School of Science and the Environment, Division of Chemistry and Environmental Science, John Dalton Building, Chester Street, Manchester, M1 5GD, UK 10.3762/bjoc.10.323 Abstract N-acyliminium ions

• electroorganic techniques and future directions. Keywords: anodic oxidation; electrochemistry; electroorganic, electrosynthesis, N-acyliminium ions; natural products; non-Kolbe oxidation; peptidomimetics; Shono oxidation; synthesis; Review N-Acyliminium ions are synthetically versatile N-Acyliminium ions [1][2

• role in reducing the diastereoselectivity of the reaction when the alkene is aryl- or alkyl-substituted. The hydration step can occur via pathway a or b to afford 17 (dr ca. 3:2). The N-acyliminium ions formed during an anodic oxidation of a silyl auxiliary can be coupled to a radical pathway using a

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• dienophile is facilitated. Yoshida, Suga and co-workers reported on the use of electrogenerated N-acyliminium ions as heterodienes in [4 + 2] cycloadditions [66]. It was found that these highly reactive species, generated from silylated carbamate 57 at −78 °C (cation pool method), undergo cycloaddition at 0

Aza-Diels–Alder reaction between N-aryl-1-oxo-1H-isoindolium ions and tert-enamides: Steric effects on reaction outcome

• Amitabh Jha,
• Ting-Yi Chou,
• Zainab ALJaroudi,
• Bobby D. Ellis and
• T. Stanley Cameron

Beilstein J. Org. Chem. 2014, 10, 848–857, doi:10.3762/bjoc.10.81

• isoindolo[2,1-a]quinolone derivatives involves N-acyliminium ions or appropriate electron-deficient Schiff bases and subsequent [4 + 2] inverse-demand hetero-Diels–Alder cycloadditions with alkenes [11][12][13][14][15][16][17]. Vinylic systems from isoeugenol [11], cyclopentadiene [12], enones [13], vinyl

• ethers [14] and enolic 1,3-diketo compounds [15], have been reported to react with N-acyliminium ions obtained either from 2-formylbenzoic acid and anilines [11][12] or from N-acyliminium ions prepared from N-arylphthalimides [13][14][15]. Nucleophilic substitution of N-aryl-3-hydroxyisoindolinones from

• analogous to the final step of imino [4 + 2] Diels–Alder reactions between N-acyliminium ions and electron-rich dienophiles are reported [13][14][15]. We synthesized eight N-aryl-3-hydroxyisoindolinones from substituted anilines and phthalic anhydride following the reported procedure [13]. Previously

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• and indoles are then added to the N-acyliminium ions 68b to provide the amidoalkylation products 69. Alternatively, the use of only persulfate at 55 °C afforded the same products. However, higher yields and better selectivities were generally observed with the photocatalytic process. Intercepted by

Carbolithiation of N-alkenyl ureas and N-alkenyl carbamates

• Julien Lefranc,
• Alberto Minassi and
• Jonathan Clayden

Beilstein J. Org. Chem. 2013, 9, 628–632, doi:10.3762/bjoc.9.70

• carbon atom β to the nitrogen atom [1][2]. The resulting intermediate iminium or N-acyliminium ions are electrophilic, and may themselves trap a nucleophile at the position α to the nitrogen substituent. However, we [3][4] and others [5][6][7] have shown that this typical reactive polarity may be

Synthesis of a library of tricyclic azepinoisoindolinones

• Bettina Miller,
• Shuli Mao,
• Kara M. George Rosenker,
• Joshua G. Pierce and
• Peter Wipf

Beilstein J. Org. Chem. 2012, 8, 1091–1097, doi:10.3762/bjoc.8.120

• synthetic building blocks, a variety of approaches for the preparation of these heterocycles have been explored [11][12][13][14][15][16][17][18]. Previously, we reported on the addition of organometallic reagents to in situ generated N-acyliminium ions [19]. This methodology applies to a variety of

A concise synthesis of 3-(1-alkenyl)isoindolin-1-ones and 5-(1-alkenyl)pyrrol-2-ones by the intermolecular coupling reactions of N-acyliminium ions with unactivated olefins

• Nianhong Lu,
• Lihong Wang,
• Zhanshan Li and
• Wei Zhang

Beilstein J. Org. Chem. 2012, 8, 192–200, doi:10.3762/bjoc.8.21

• the coupling reactions of N-acyliminium ions produced from 3-hydroxyisoindol-1-ones or 5-hydroxy-1-pyrrol-2-ones with unactivated olefins in the presence of BF3·OEt2 at room temperature. For most of the olefins, the reactions afforded the Csp3–Csp2 cross-coupling products, but for the α-methylstyrene

• and 1-hexene, the Csp3–Csp3 cross-coupling products were obtained. Keywords: 3-(1-alkenyl)isoindol-1-ones; 5-(1-alkenyl)pyrrol-2-ones; coupling reaction; 2,3-dihydro-3-hydroxyisoindol-1-one; 2,5-dihydro-5-hydroxypyrrol-2-one; N-acyliminium ions; Introduction The coupling of alcohols with alkynes

• ]. We have long been interested in the reactions of N-acyliminium ions produced easily by the Brønsted acid and Lewis acid catalyzed dehydroxylation of α-hydroxyamides [12][13][14]. The high electrophilicity of these species is very suitable for electrophilic addition to carbon–carbon multiple bonds

A practical microreactor for electrochemistry in flow

• Kevin Watts,
• William Gattrell and
• Thomas Wirth

Beilstein J. Org. Chem. 2011, 7, 1108–1114, doi:10.3762/bjoc.7.127

• trapped immediately after generation. In the "cation flow" method, a carbocation is generated continuously in a flow system by low temperature electrolysis. The generation of the cation can be monitored by a FTIR spectrometer in the flow system. The electrochemically generated N-acyliminium ions can then

• the product selectivity. Cycloadditions using the N-acyliminium ions as heterodienes with a variety of dienophiles, such as alkenes and alkynes, give the corresponding [4 + 2] cycloaddition products in high yields [10]. The same authors also reported a successful polymer synthesis using the same

• technique by adding a monomer to the initiator (N-acyliminium ions) followed by micromixing and the addition of the terminator (diisopropylamine) in a subsequent micromixer. This was considered to be a superior technique to the batch method as the molecular weight distribution of the polymer 3 decreased in

A convenient allylsilane- N-acyliminium route toward indolizidine and quinolizidine alkaloids

• Roland Remuson

Beilstein J. Org. Chem. 2007, 3, No. 32, doi:10.1186/1860-5397-3-32

• ] The allylsilyl functional group is a weak carbon nucleophile for trapping N-acyliminium ions, thus providing a useful method for intramolecular carbon-carbon bond formation. [28][29] We have applied this methodology towards the synthesis of indolizidine alkaloids. (vide supra) We describe here a new